Journal on Policy and Complex Systems
2.1 Agent and State Variable
The agent in our model was defined as an ancient person with the following variables .
Identity ( ID ) Number and Spatial Placement : The following information was assigned to an agent : an ID number and a coordinate position [ X : 50 cells , Y : 50 cells ] within a two-dimensional space . This space represented the main island of Okinawa . Within our simulation model , the simulation space represented a very abstract space . This meant that the space was not directly related to real geographical space , because we mainly focused on discussing the relative diffusion of trait genes , mtD- NA , and pottery style and agriculture . Considering the gene flow and pottery style relative to the speed of agricultural diffusion , the abstract space was sufficient for considering the issues at hand . The size of the space within our simulation was defined by the speed of diffusion of agriculture as described below .
Sex : The agent was male or female .
Life Expectancy and Age : Upon creation ( birth ), an agent was given an individual life expectancy based on the mortality table . If the age of the agent exceeded the life expectancy , the agent was removed ( died ). Supposing that the mortality table has not changed from ancient times up until the modern period , we created this by reflecting an infant mortality rate of 20 % up to recent years on that of people of the Jomon period ( Nagaoka , Sawada , & Hirata , 2008 ). Food Production System : The food production system variables were hunting and gathering or agriculture . This system changed from hunting and gathering to agriculture through the diffusion of agriculture based on the assumption that the difficulty of food obtained by hunting and gathering in the late Shell midden period , an antecedent of the Gusuku period , introduced an opportunity for this conversion process ( Takamiya , 2002 ). However , we assumed that the opposite condition did not hold , because there is no evidence of the diffusion of hunting and gathering during this period .
Marriage Institution : The marriage institution variable for the male agent was monogamous or polygamous . To date , the type of marriage institutions that prevailed during the Shell midden period and the Gusuku period have not been ascertained . However , in the Yayoi period ( 300 BC – 250 AD ) of the Japanese mainland , it has been assumed that polygamous marriage occurred based on descriptions of this type of marriage contained in “ Gishi-Wazin-Den ,” an ancient Chinese text on the Yayoi period customs . According to this text , some men of high status had four or five wives , and there were even some men of normal
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